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GIO(4) Device Drivers Manual (sgi) GIO(4)


gioGraphics I/O GIO bus


gio0 at imc0


The gio bus is a bus for connecting high-speed peripherals to the main memory and CPU. The devices themselves are typically (but not necessarily) connected to the hpc(4) peripheral controller, and memory and CPU are accessed through the imc(4) system controller. The gio bus is found on the Indigo, Indy, Challenge S, Challenge M, and Indigo2 machines and exists in three incarnations: GIO32, GIO32-bis, and GIO64.
The devices currently supported under OpenBSD are:
SGI Express graphics
SGI High performance Peripheral Controller
SGI Impact (aka Mardigras) graphics
SGI Light graphics
SGI Newport graphics


imc(4), intro(4)


Challenge S systems may use only one gio DMA-capable expansion card, despite having two slots. Cards based on the hpc(4) controller, such as the GIO32 SCSI and E++ Ethernet adapters, must be placed in slot 1 (closest to the side of the case). All other cards must be placed in slot 0 (adjacent to the memory banks).
Indigo2 and Challenge M systems contain either three or four GIO64 connectors, depending on the model. However, in both cases only two electrically distinct slots are present. Therefore, distinct expansion cards may not share physical connectors associated with the same slot. On the other hand, these apparently redundant slot connectors allow multiple board assemblies to draw more power from the bus, and also helps mix gio and EISA boards in the same chassis. In all systems, the upper two GIO64 connectors are GIO slot 1, while the lower connectors (either one or two of them) are GIO slot 0.
April 18, 2012 OpenBSD-current